Not my first time on Norwegian, went there without any expectation. My best experience so far. Check-in was fast, however, I was later in the process which might explain how I end up on the ship from the shuttle in about 45 min.
The observation deck on 15 was really pleasant, my favourite place to read a book. However, I didn't like the front since open to the buffet so noise can become a problem. I will say that the noise level was a problem in most public space when they get crowded.
Circulation in the ship was easy didn't take long to figure out where is the front from the back base on where you are. There is more activity that requires a fee on that ship which includes go-kart, laser tag and one show. That being said those activities would have cost me more on land so I'm too mad about it and did all of those!
As long as you keep organize studios aren't too bad. No more led light change colour, which I never end up using so not a big lost. The virtual windows were the best addition. They change the colour skim of the cabin from whit only white to white with a shade of light brown. Once used to it didn't notice it anymore. Access to studio lounge is a plus if you like to have juice, coffee or tea and cookies. It is right you do not need to go fare.